The invention relates to integrated chip optical devices and is particularly related to such devices where optical components including at least one waveguide are formed on a substrate.
In order to make external optical connections to such an integrated chip optical device, it may be required to join off chip optical fibres to waveguides onchip adjacent an edge of the chip. To achieve satisfactory optical function at such a junction it is desirable that the chip has high edge quality where any such junction is to be formed.
It is an object of the present invention to provide an improved method of forming an integrated chip optical device as well as an improved device, having high edge quality for such external optical junctions.
The invention provides a method of forming an integrated chip optical device comprising forming a plurality of optical components on a substrate including at least one waveguide extending over a surface of the substrate to an edge of the device, forming a protective layer over at least part of said surface including an edge region in which said edge is located, selectively removing the protective coating from certain regions of said surface while leaving the protective coating over said edge region, and polishing the edge of the device in said edge region to provide high edge quality enabling said waveguide to be abutted against and joined to an offchip optical fibre.
Preferably said protective coating comprises a hard setting photoresist.
Preferably said protective coating is spun over the surface of the chip.
Preferably the protective coating is selectively removed using photolithography techniques.
Preferably a plurality of waveguides extend to said edge and each is secured to an offchip optical fibre.
Preferably each said waveguide is secured to an offchip fibre by adhesive with the fibre abutting the respective waveguide at said edge.
Preferably said edge is polished at an angle of inclination to the surface of the chip so as to reduce reflections at the edge passing along the waveguide or fibre.
In some embodiments said protective coating is removed from regions of the chip on which optical components are formed so as to leave said optical components uncovered by the protective layer.
The invention also provides an integrated chip optical device comprising a plurality of optical components on a substrate including at least one waveguide extending over a surface of the substrate to an edge of the device, a protective layer being formed selectively over part of the surface of the chip adjacent an edge region in which said edge is located, said edge being polished to provide a high edge quality thereby forming a junction face at the edge of the chip for abutting said waveguide to an offchip optical fibre.
Preferably said edge is polished at an angle of inclination to the surface of the chip so that the external face of the waveguide is not perpendicular to the length of the waveguide.
Preferably one or more offchip optical fibres abut a respective waveguide at said edge and are secured thereto by adhesive.